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10-2 Cell Division
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In eukaryotes, cell division occurs in two major
stages.
The first stage, division of the cell nucleus, is
called mitosis.
The second stage, division of the cell cytoplasm, is
called cytokinesis.
Cell Division
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Chromosomes
Chromosomes
Genetic information is passed from one
generation to the next on chromosomes.
Before cell division, each chromosome is
duplicated, or copied.
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Chromosomes
Each chromosome consists of two identical “sister” chromatids.
Each pair of chromatidsis attached at an area called the centromere.
Sister chromatids
Centromere
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Chromosomes
When the cell divides, the chromatidsseparate.
Each new cell gets one chromatid.
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The Cell Cycle
What are the main events of the cell
cycle?
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The Cell Cycle
During the cell cycle:
• a cell grows
• prepares for division
• divides to form two daughter cells, each
of which begins the cycle again
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The Cell Cycle
The cell cycle consists of four phases:
• G1 (First Gap Phase)
• S Phase
• G2 (Second Gap Phase)
• M Phase
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Events of the Cell Cycle
Events of the Cell Cycle
During G1, the cell
• increases in size
• synthesizes new proteins and organelles
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Events of the Cell Cycle
During the S phase,
• chromosomes are replicated
• DNA synthesis takes place
Once a cell enters the S phase, it usually completes the rest of the cell cycle.
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Events of the Cell Cycle
During G2 Phase (Second Gap Phase)
• organelles and molecules required for cell
division are produced
• Once G2 is complete, the cell is ready to start the
M phase—Mitosis
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Cell Cycle
Events of the Cell Cycle
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Mitosis
What are the four phases of mitosis?
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Mitosis
Mitosis
Biologists divide the events of mitosis
into four phases:
• Prophase
• Metaphase
• Anaphase
• Telophase
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Mitosis
Mitosis
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Section 10-2
ProphaseSpindle
forming
Chromosomes
(paired
chromatids)Centromere
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Mitosis
Prophase
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Mitosis
Prophase
Prophase is the first and
longest phase of mitosis.
The centrioles separate
and take up positions on
opposite sides of the
nucleus.
Spindle
forming
CentromereChromosomes
(paired
chromatids)
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Mitosis
The centrioles lie in a region called the centrosome.
The centrosome helps to organize the spindle, a fanlike microtubule structure that helps separate the chromosomes.
Spindle
forming
CentromereChromosomes
(paired
chromatids)
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Mitosis
Chromatin condenses
into chromosomes.
The centrioles separate
and a spindle begins to
form.
The nuclear envelope
breaks down.
Spindle
forming
CentromereChromosomes
(paired
chromatids)
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Centriole
Centriole
Spindle
Mitosis
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Metaphase
Metaphase
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Mitosis
Metaphase
The second phase of mitosis is metaphase.
The chromosomes line up across the center of the cell.
Microtubules connect the centromere of each chromosome to the poles of the spindle.
Centriole
Spindle
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Individual
chromosomes
Anaphase
Mitosis
Anaphase
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Mitosis
Anaphase
Anaphase is the third phase of mitosis.
The sister chromatidsseparate into individual chromosomes.
The chromosomes continue to move until they have separated into two groups.
Individual
chromosomes
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Nuclear
envelope
reforming
Telophase
Mitosis
Telophase
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Mitosis
Telophase
Telophase is the
fourth and final phase
of mitosis.
Chromosomes gather
at opposite ends of the
cell and lose their
distinct shape.
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Mitosis
A new nuclear envelope
forms around each cluster
of chromosomes.
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Cytokinesis
Cytokinesis
Cytokinesis
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Cytokinesis
During cytokinesis, the
cytoplasm pinches in
half.
Each daughter cell has
an identical set of
duplicate chromosomes
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Cytokinesis in Plants
In plants, a structure known as the cell plate forms
midway between the divided nuclei.
Cell wallCell plate
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Cytokinesis in Plants
The cell plate gradually develops into a separating
membrane.
A cell wall then begins to appear in the cell plate.
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